Anyone know what causes this?

[Phil Nelson]

My Hallicrafters T-67 had Barkhausen interference. The cure was to substitute a horizontal output tube that didn't oscillate.

It does seem odd that you'd have four sets with that identical problem, but what do I know.

One of my old TV books has a good discussion of Barkhausen. Besides subbing the tube, they suggest reducing the drive, or even putting a small circular magnet around the output tube and rotating it until the oscillation is suppressed.

I don't know if what you have is Barkhausen effect, but those are all pretty easy things to try.

[Phil Nelson]

P.S. Reading an adjacent section in that book, they say that simple misadjustment of the horizontal drive makes a white line (yours looks white to me), while Barkhausen creates a dark line. Which favors the drive explanation, I guess.

OK, now I'll shut up :-)

[Charlie]

After hearing everyone's input (and thanks to all for it), I'm going with the idea that the Horz drive needs to be turned down. This is what I figured from the beginning, but was curious of what everyone here thought.

My sets that produce the white line all had new lytics and caps replaced, and likely new output tubes. I never checked or adjusted the drive in those sets. Perhaps I should have.

As mentioned before, I've never dealt with this in a color set... and I'd guess it's because I try to make sure that the drive is set correctly so not to roast a flyback.

Thanks again for the comments. I'll let you guys know what I find as soon as I pull the backs off the sets.

[Don Lindsly]

There is no horizontal drive adjustment on the Philco Diamond D.

[Charlie]

Originally Posted by Don Lindsly

There is no horizontal drive adjustment on the Philco Diamond D.

Well then... that might present a problem! Oh well... glad you told me that... or I would have been pullin my hair out tryin to find it!